wifi: rtl8xxxu: rtl8xxxu_rx_complete(): remove unnecessary return

Remove a return statement at the end of a void function.

This fixes a checkpatch warning.

WARNING: void function return statements are not generally useful
6206: FILE: ./drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c:6206:
+  return;
+}

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Reviewed-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230427185936.923777-1-martin@kaiser.cx